Not applicable
1. Field of the Invention
The present invention generally relates to an orientation and locator system including a coupling sub to secure a tool within a receiver sub previously disposed within a string of casing installed in the borehole and more particularly, to a coupling sub that is installed and removed from the receiver sub in the casing string. Furthermore, the present invention relates to, a coupling sub for securing, positioning, and removing a whipstock at a known location within in a cased borehole.
2. Description of the Related Art
It is common for well operations to be conducted at a known location within the bore of a well. This location may be relative to a formation, to a previously drilled well bore, or to a previously conducted well operation. For example, it is important to know the depth of a previous well operation. However, measurements from the surface are often imprecise. Although it is typical to count the sections of pipe in the pipe string as they are run into the borehole to determine the depth of a well tool mounted on the end of the pipe string, the length of the pipe string may vary due to stretch under its own weight or due to downhole temperatures. This variance is magnified when the pipe string is increased in length, such as several thousand feet. It is not uncommon for the well tool to be off by several feet when depth is measured from the surface.
Many well operations require locating a particular depth and azimuth in the borehole for conducting a new well operation. One such well operation is the drilling of one or more lateral boreholes. One typical sidetracking operation for drilling a lateral wellbore from a new or existing wellbore includes running a packer or anchor into the wellbore on wireline or on coiled tubing and then setting the packer or anchor within the wellbore. The packer or anchor is set at a known depth in the well by determining the length of the wireline or coiled tubing run into the wellbore. A second run or trip is made into the wellbore to determine the orientation of the packer or anchor. Once this orientation is known, a latch and whipstock are properly oriented and run into the wellbore during a third trip wherein the latch and whipstock are seated on the packer or anchor. One or more mills are then run into the wellbore on a drill string to mill a window in the casing of the wellbore. The whipstock is then retrieved. Subsequent trips into the wellbore may then be made to drill the lateral borehole or to install a deflector or other equipment for down hole operations.
In conventional sidetracking operations, although the depth of the packer or anchor used to support the whipstock is known, the orientation of the packer or anchor within the wellbore may not be known. Thus, a subsequent trip must be made into the wellbore to determine the orientation of the packer or anchor using an orientation tool. The packer or anchor has a receptacle with an upwardly facing orienting surface which engages and orients the orientation tool stabbed into the packer or anchor. The orientation tool then determines the orientation of the packer or anchor within the wellbore. Once the orientation of the packer or anchor has been established, the orientation of the latch, whipstock and mill to be subsequently disposed in the wellbore is then adjusted at the surface so as to be properly oriented when run into the wellbore. The latch, whipstock and mill are then run into the wellbore and stabbed and latched into the packer or anchor such that the face of the whipstock is properly directed for milling the window and drilling the lateral borehole.
Since the packer or anchor are not oriented prior to their being set, the receptacle having the orienting surface and a mating connector may have an orientation that could lead to the receptacle being damaged during future operations. If the receptacle is damaged, it will not be possible to use it for orientation and latching of a subsequent well operation.
It is preferred to avoid numerous trips into the wellbore for the sidetracking operation. A one trip milling system is disclosed in U.S. Pat. Nos. 5,771,972 and 5,894,889. See also, U.S. Pat. No. 4,397,355.
In a sidetracking operation, the packer or anchor serves as a downhole well tool which anchors the whipstock within the cased borehole against the compression, tension, and torque caused by the milling of the window and the drilling of the lateral borehole. The packer and anchor have slips and cones which expand outward to bite into the cased borehole wall to anchor the whipstock. A packer also includes packing elements which are compressed during the setting operation to expand outwardly into engagement with the casing thereby sealing the annulus between the packer and the casing. The packer is used for zone isolation so as to isolate the production below the packer from the lateral borehole.
An anchor without a packing element is typically used where the formation in the primary wellbore and the formation in the lateral wellbore have substantially the same pressure and thus the productions can be commingled since there is no zone pressure differentiation because the lower zone has substantially the same formation pressure as that being drilled for the lateral. In the following description, it should be appreciated that a packer includes the anchoring functions of an anchor.
The packer may be a retrievable packer or a permanent big bore packer. A retrievable packer is retrievable and closes off the wellbore while a permanent big bore packer has an inner mandrel forming a flowbore through the packer allowing access to that portion of the wellbore below the packer. The mandrel of the big bore packer also serves as a seal bore for sealing engagement with another well tool, such as a whipstock, bridge plug, production tubing, or liner hanger. The retrievable packer includes its own setting mechanism and is more robust than a permanent big bore packer because its components may be sized to include the entire wellbore since the retrievable anchor and packer does not have a bore through it and need not be a thin walled member.
One apparatus and method for determining and setting the proper orientation and depth in a wellbore is described in U.S. Pat. No. 5,871,046. A whipstock anchor is run with the casing string to the desired depth as the well is drilled and the casing string is cemented into the new wellbore. A tool string is run into the wellbore to determine the orientation of the whipstock anchor. A whipstock stinger is oriented and disposed on the whipstock at the surface, and then the assembly is lowered and secured to the whipstock anchor. The whipstock stinger has an orienting lug which engages an orienting groove on the whipstock anchor. The whipstock stinger is thereby oriented on the whipstock anchor to cause the face of the whipstock to be positioned in the desired direction for drilling. The whipstock stinger may be in two parts allowing the upper part to be rotated for orientation in the wellbore. The anchor portion of the apparatus of the ""046 patent is structured such that it restricts the flowbore of the casing string. Furthermore, because of this restriction, if subsequent anchors are to be set beyond a primary anchor, they must accommodate progressively smaller gauges. There is no provision in the ""046 patent to allow a latching tool engage one anchor, and then pass through en route to engagement with another anchor further downhole.
U.S. Pat. No. 5,467,819 describes an apparatus and method which includes securing an anchor in a cased wellbore. The anchor may include a big bore packer. The wall of a big bore packer is roughly the same as that of a liner hanger. The anchor has a tubular body with a bore therethrough and slips for securing the anchor to the casing. The anchor is set by a releasable setting tool. After the anchor is set, the setting tool is retrieved. A survey tool is oriented and mounted on a latch to run a survey and determine the orientation of the anchor. A mill, whipstock, coupling and a latch or mandrel with orientation sleeve connected to the lower end of the whipstock are assembled with the coupling allowing the whipstock to be properly oriented on the orientation sleeve. The assembly is then lowered into the wellbore with a lug on the orientation sleeve engaging an inclined surface on the anchor to orient the assembly within the wellbore. The window is milled and then the lateral is drilled. If it is desirable to drill another lateral borehole, the whipstock may be reoriented at the surface using the coupling and the assembly lowered into the wellbore and re-engaged with the anchor for drilling another lateral borehole.
U.S. Pat. No. 5,592,991 discloses another apparatus and method for installing a whipstock. A permanent big bore packer having an inner seal bore mandrel and a releasable setting tool for the packer allows the setting tool to be retrieved to avoid potential leak paths through the setting mechanism after tubing is later sealingly mounted in the packer. An assembly of the packer, releasable setting tool, whipstock, and one or more mills is lowered into the existing wellbore. The packer may be located above or below the removable setting tool. A survey tool may be run with the assembly for proper orientation of the whipstock. A lug and orienting surface are provided with the packer for orienting a subsequent well tool. The packer is then set and the window in the casing is milled. The whipstock and setting tool are then retrieved together leaving the big bore packer with the seal bore for sealingly receiving a tubing string so that production can be obtained below the packer. One disadvantage of the big bore packer is that its bore size will not allow the next conventional smaller sized casing to be run through its bore requiring an even smaller sized casing.
Furthermore, U.S. Pat. No. 5,592,991 describes the use of a big bore packer as a reference device. However, once the releasable setting tool and whipstock are removed from the big bore packer, the packer no longer has sealing integrity. The big bore packer only seals the wellbore after another assembly is lowered into the well and a stinger is received by the big bore packer to create or establish sealing integrity. The big bore packer does double duty, first it serves as the anchor for the milling operation and then it becomes a permanent packer for the completion.
In both the ""819 and ""991 patents, the whipstock assembly must latch into the packer or anchor to anchor the whipstock and withstand the compression, tension, and torque applied during the milling of the window and the drilling of the lateral borehole. Further, the use of a big bore packer requires a packer assembly which can withstand a 5,000 psi pressure differential and thus all of its components must have a minimum 5,000 psi burst and collapse capability.
The big bore packer has the additional disadvantage of having a mandrel extending through it and on which is mounted the cones for activating the slips of the packer. The mandrel is subsequently used as a seal bore which is then used for sealing with a tubing string. This mandrel is not only an additional mechanical part but requires a reduction in the diameter of the bore of the packer. Furthermore, to remove restrictions from the borehole following operations, an additional trip downhole to retrieve the anchor or packer is required.
When sidetracking operations are conducted using systems of the ""819 and ""991 patents, numerous trips are required into the wellbore. A packer is first run into the wellbore on wireline or on coiled tubing and then is set within the wellbore. A second run or trip is made into the wellbore to determine the orientation of the packer. Once this orientation is known, a latch and whipstock are properly oriented and run into the wellbore during a third trip wherein the latch and whipstock are seated on the packer. At this point, a window is milled in the casing of the wellbore. The whipstock is then retrieved. Subsequent trips into the wellbore are then made to install a deflector or other equipment to drill a rat hole to initiate the drilling of the lateral borehole.
Further, in conventional sidetracking operations, the packer or anchor, used to support the whipstock, are run and set in the wellbore without knowing their orientation within the wellbore. Thus, a subsequent trip must be made into the wellbore to determine the orientation of the packer or anchor using an orientation member. The packer or anchor has a receptacle with an upwardly facing mule shoe orienting surface to orient a subsequent apparatus stabbed into the packer or anchor. Once the orientation of the packer or anchor has been established, a latch, whipstock and mill can be run into the wellbore and stabbed and latched into the packer or anchor.
Since the packer or anchor is not oriented prior to being set, the receptacle, having the mule shoe orienting surface and a mating connector, may have an orientation that could lead to the receptacle being damaged during future operations. If the receptacle is damaged too badly, then it will not be possible thereafter to use it for orientation and latching of additional well tools.
A well orientation and depth location device is disclosed in U.S. patent application Ser. No. 09/575,091 filed May 19, 2000 and entitled Anchor Apparatus and Method, which corresponds to UK Patent Application GB 2 351 303, published Dec. 27, 2000, hereby incorporated herein by reference. The ""091 application discloses a well location anchor that is deployed upon a tool string and is set at a desired depth and azimuth to properly locate any well operations that may subsequently occur. The anchor includes an integral means to resist any axial or rotational loads that may be transmitted to it during any operations that may utilize the anchor""s location capabilities. Because the anchor is run following drilling and casing operations, it is set within the existing borehole or casing string and restricts the movement of large gage tools or drillstring therethrough. Because of this, the anchor locator of the ""091 application significantly limits further exploration and production of wells in which it is used.
The present invention overcomes the deficiencies of the prior art.
An orientation and locator system including a receiver sub disposed in and installed with a casing string in the borehole. The receiver sub has azimuth and depth profiles for positively locating a predetermined position within the borehole. The profiles are within the inside diameter of the casing string and do not restrict the flowbore of the casing. The orientation and locator system further includes a coupling sub attached to a well tool and adapted to engage the casing receiver sub to orient and locate the well tool within the borehole for conducting a well operation. The coupling sub has an alignment key and a plurality of dogs for engaging the azimuth and depth profiles, respectively. Further, the coupling sub may pass completely through the receiver sub en route to another receiver sub located in the casing string further downhole. The coupling sub and receiver sub are configured such that they may be engaged whether the coupling sub is passing upstream or downstream through the casing string.
The present invention overcomes the deficiencies of the prior art by providing a location system incorporating a receiver sub that is disposed upon and installed with the casing string. Other objects and advantages of the invention will appear from the following description.